Wideband Amplifier Tuning

ABSTRACT

Circuit and methods using a single low-noise amplifier (LNA) to provide amplification for a wide band of RF frequencies while maintaining high gain and a low noise factor. Embodiments include an amplifier circuit including an input signal path for receiving a wideband RF signal; a switched inductor tuning block coupled to the input signal path and configured to selectively couple one of a plurality of inductances to the input signal path; and an amplifier coupled to the switched inductor tuning block and configured to receive the RF signal after passage through the selected coupled inductance. The switched inductor tuning block includes a plurality of selectable branches, each including an RF input switch; an RF output switch; an inductor coupled between the RF input switch and the RF output switch; and first and second shunt switches coupled between a respective terminal of the inductor and circuit ground.

BACKGROUND (1) Technical Field

This invention relates to electronic circuitry, and more particularly toradio frequency low noise amplifiers.

(2) Background

Many modern electronic systems include radio frequency (RF) receivers;examples include personal computers, tablet computers, wireless networkcomponents, televisions, cable system “set top” boxes, radar systems,and cellular telephones. Many RF receivers are paired with RFtransmitters in transceivers, which often are quite complex two-wayradios. In some cases, RF transceivers are capable of transmitting andreceiving across multiple frequencies in multiple bands; for instance,in the United States, the 2.4 GHz band is divided into 14 frequencyranges (channels) spaced about 5 MHz apart. As another example, a modern“smart telephone” may include RF transceiver circuitry capable ofconcurrently operating on different cellular communications systems(e.g., GSM, CDMA, and LTE), on different wireless network frequenciesand protocols (e.g., IEEE 802.11abgn at 2.4 GHz and 5 GHz), and on“personal” area networks (e.g., Bluetooth based systems).

The receiver-side of an RF transceiver includes a “front end” thatgenerally includes at least one low noise amplifier (“LNA”). An LNA isresponsible for providing the first stage of amplification for areceived RF signal. In many applications, multiple LNAs are needed tocover all frequencies in one or more bands. For example, FIG. 1 is blockdiagram of a simplified RF receiver 100 having multiple LNAs. An RFsignal source 102, such as one or more antennas, provides an RF signalto n LNAs (LNA1-LNAn), each of which provides an amplified RF signal to“downstream” circuits such as down-conversion and baseband circuitry104_1, 104_n. In the illustrated example, LNA1-LNAn may be individuallyenabled or disabled by a corresponding control signal, ENABLE1-ENABLEn.Additional components not shown in FIG. 1 may include, for example (1)RF switches, filters, and impedance matching circuitry before LNA1-LNAn,and (2) attenuators, filters, and impedance matching circuitry afterLNA1-LNAn.

The operational characteristics of an LNA are very important to theoverall quality of an RF receiver, particularly low noise, gain flatness(i.e., signal gain variation across frequency), linearity, inputmatching, and output matching. However, it is known that low noise, gainflatness, linearity, input matching, and output matching are hard toachieve over a wide band. Accordingly, multiple narrow-band,single-stage LNAs are generally used to cover all frequency bandsrequired of an RF transceiver. Typically, each LNA requires dedicatedanalog circuitry, such as inductors, capacitors, bias voltagegenerators, signal level shifters, matching networks, etc.

Modern RF receivers, whether stand-alone or as part of a transceiver,are generally embodied in an integrated circuit (IC) die. As in manyareas of modern electronics, a smaller die size is a key goal for costreduction of RF products. However, RF receivers that include multiplenarrow-band, single-stage LNAs consume a significant die area for all ofthe necessary dedicated analog circuitry.

Accordingly, there is a need for compact LNA circuitry that overcomesthe limitations of the prior art, particularly with respect toaccommodating a wide band of frequencies in a compact circuit design.Embodiments of the present invention provide such circuitry, as well asadditional benefits.

SUMMARY

The invention encompasses circuit and methods using a single low-noiseamplifier (LNA) to provide amplification for a wide band of RFfrequencies while maintaining high gain and a low noise factor (NF).

Embodiments include an amplifier circuit including an input signal pathfor receiving a wideband radio frequency (RF) signal; a switchedinductor tuning block coupled to the input signal path and configured toselectively couple one of a plurality of inductances in series with theinput signal path; and an amplifier having an input coupled to theswitched inductor tuning block and configured to receive the RF signalafter passage through the selected coupled inductance, and an output forproviding an amplified version of the RF signal. The switched inductortuning block includes a plurality of selectable branches, each branchincluding: an RF signal input switch; an RF signal output switch; aninductor coupled between the RF signal input switch and the RF signaloutput switch; a first shunt switch coupled between a first terminal ofthe inductor and circuit ground; and a second shunt switch coupledbetween a second terminal of the inductor and circuit ground.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is block diagram of a simplified RF receiver having multipleLNAs.

FIG. 2 is a block diagram of one embodiment of a wide-band single-LNAamplifier circuit in accordance with the present invention.

FIG. 3 is a schematic diagram of one embodiment of a switched inductortuning block suitable for use in the amplifier circuit of FIG. 2.

FIG. 4 is a circuit diagram of one embodiment of one branch X for theswitched inductor tuning block of FIG. 3, using field effect transistors(FETs) for switches.

FIG. 5A is a block diagram showing a first configuration of multipleLNAs coupled to the RF_(OUT) port of a switched inductor tuning blockthrough series switches.

FIG. 5B is a block diagram showing a second configuration of multipleLNAs coupled to a switched inductor tuning block through a switchingmatrix.

FIG. 6 illustrates an exemplary prior art wireless communicationenvironment including different wireless communication systems, and mayinclude one or more mobile wireless devices.

FIG. 7 is a block diagram of a transceiver that might be used in awireless device, such as a cellular telephone, and which maybeneficially incorporate an embodiment of the present invention forimproved performance at a small IC chip size.

FIG. 8 is a process flow chart showing one method of providing awideband radio frequency (RF) signal to at least one amplifier.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

The invention encompasses circuit and methods using a single low-noiseamplifier (LNA) to provide amplification for a wide band of RFfrequencies while maintaining high gain and a low noise factor (NF).

FIG. 2 is a block diagram of one embodiment of a wide-band single-LNAamplifier circuit 200 in accordance with the present invention. Radiofrequency (RF) input signals, such as from one or more antennas, may beapplied to one or more input ports of an RF input switch 202. The RFinput switch 202 selectively couples one or more of the RF input signalsto a Direct Gain Path and/or to an Attenuated Path. In some embodiments,a matching network 204 may be coupled to one input port of the RF inputswitch 202, and such that the RF input switch 202 can selectively couplethe matching network 204 to the Direct Gain Path and/or the AttenuatedPath in combination with selection of an RF input signal to the samepath, thus putting the matching network 204 in-circuit with the selectedpath, thereby acting upon the selected RF input signal.

The Attenuated Path is shown coupled to a path switch 206 through aninput attenuator 208. The input attenuator 208 typically allowsselection of a one or more levels of attenuation (useful if a strong RFinput signal is present), and in some embodiments may allow for internalbypassing of any attenuation. The path switch 206 allows the selected RFsignal from the input attenuator 208 to be switched to a Bypass Path orto an Attenuated Gain Path.

Selected RF signals switched to the Bypass Path by the path switch 206may be applied to an optional output attenuator 210, which typicallyallows selection of a one or more levels of attenuation and in someembodiments may allow for internal bypassing of any attenuation. TheBypass Path is coupled to an output switch 212, the output of which isan RF_(OUT) signal.

Selected RF signals switched to the Attenuated Gain Path by the pathswitch 206 are coupled to the input of a switched inductor tuning block214. RF signals switch to the Direct Gain Path by the RF input switch202 are also coupled to the input of a switched inductor tuning block214, described below in greater detail. The output of the switchedinductor tuning block 214 is coupled through a DC blocking capacitor C1to the input of a signal LNA 216. The LNA 216 may be of differentdesigns as needed for particular applications. Examples of low-noiseamplifiers that may be used for the LNA 216 are described in U.S. Pat.No. 9,929,701, issued Mar. 27, 2018, entitled “LNA with ProgrammableLinearity”, assigned the assignee of the present invention andincorporated herein by reference.

The output of the LNA 216 is coupled to a DC blocking and outputimpedance matching capacitor C2, which may have a bypassable variablecapacitor C3 coupled in parallel to provide for output impedance tuning.The capacitors C2 and C3 are coupled to an output attenuator 218. Theoutput attenuator 218 typically allows selection of a one or more levelsof attenuation and in some embodiments may allow for internal bypassingof any attenuation. The output of the output attenuator 218 is coupledto the output switch 212. Accordingly, the output switch 212 mayselectively output either an amplified RF signal from the LNA 216, or aselected RF signal from the Bypass Path. In the illustrated example, theAttenuated Gain Path and the Bypass Path are selected by the path switch206 and the output switch 212 for RF signal propagation.

A tunable load matching circuit 220 coupled to the output of the LNA 216allows the output impedance of the amplifier circuit 200 to be matchedto a load coupled to the RF_(OUT) port of the output switch 212. In theillustrated example, the tunable load matching circuit 220 includes aninductor L1 (shown as fixed, but may be adjustable) coupled to a powersupply V_(DD), a tunable and selectable shunt capacitance C4, and atunable and selectable resistance R1. As is known in the art,alternative circuits may be used for the tunable load matching circuit220 as needed for specific applications.

The LNA 216 may be coupled (e.g., to a ground terminal of the LNA 216)to a bypassable and adjustable source degeneration inductor circuit 222,which in turn is coupled to circuit ground. The bypassable andadjustable source degeneration inductor circuit 222 includes anadjustable inductor L2 that allows various levels (including zero, ifbypassed) of inductance to be coupled to the internal circuitry of theLNA 216 to adjust input matching as may be needed for specificapplications, achieve gain tuning, and, in most cases, provide goodlinearity.

Similarly, the LNA 216 may be coupled (e.g., to a ground terminal of theLNA 216) to a tunable and selectable capacitance circuit 224, which inturn is coupled to the input of LNA 216. The tunable and selectablecapacitance circuit 224 includes an adjustable capacitor C5 that allowsvarious levels (including zero) of capacitance to be coupled to theinput and internal circuitry of the LNA 216 to adjust input matching forthe LNA 216 as may be needed for specific applications.

All switching of the illustrated switches may be by an amplifiercontroller (not shown), which sets the state of the switches (as well asbias levels within the LNA 216) based on, for example, informationregarding the types of RF signals that will be received by the amplifiercircuit 200, the content carried by the RF signals, and/or based on usercommands to select one or more RF bands or channels. The amplifiercontroller may be a general-purpose processor capable of receivingcommands and processing the commands to generate control signals to theLNA 216 and illustrated associated switches shown in FIG. 2.Alternatively, the amplifier controller may be a dedicated processorspecially designed for generating such control signals. In some cases,the amplifier controller may be as simple as a logic block with look-uptable.

Example Switched Inductor Tuning Block

While some of the RF input signals applied to the RF input switch 202may be constrained to a relatively narrow band by design, to accommodateintegrated circuit (IC) customers with widely varying specifications, itis useful to design one or more ports of the RF input switch 202 to beable to accommodate a wide frequency range (e.g., about 1.4 GHz to about2.7 GHz, a 1300 MHz total bandwidth) without needing multiple LNAs.Avoiding multiple LNAs results in a smaller, more economical IC chip.However, it is important to maintain good gain (e.g., at least about17-19 dB, and at least about 20 dB in some applications) and a low noisefactor (e.g., less than about 1.7 dB, and less than about 1.2 dB in someapplications) over such a wideband signal. Such specifications have notbeen found to be achievable using a single LNA with most conventionaldesign techniques while minimizing IC chip size. For example, in modeledcircuits, optimizing a conventional single-LNA amplifier for good gainand NF performance at one end of the wideband (e.g., either the 2.7 GHzend or the 1.4 GHz end of the example frequency range mentioned above)and adjusting conventional tuning components for tuning at the other endof the wideband (e.g., either the 1.4 GHz end or the 2.7 GHz end of theexample frequency range mentioned above) results in unacceptableperformance degradation, especially for gain (less than about 18 dB atone end).

Accordingly, allowing a wideband port WB for the RF input switch 202requires careful consideration of the overall architecture of theamplifier circuit 200. The solution provided by the present invention isthe switched inductor tuning block 214 before the input to the LNA 216of FIG. 2. The switched inductor tuning block 214 allows for theintroduction of two or more tuning (impedance matching) inductors thatcan be optimized for sub-bands of a wideband RF input signal with littledegradation of gain or increase in noise figure.

FIG. 3 is a schematic diagram 300 of one embodiment of a switchedinductor tuning block 214 suitable for use in the amplifier circuit 200of FIG. 2. The switched inductor tuning block 214 includes circuitbranches 1 to n, where n≥2. Each circuit branch X of the n circuitbranches includes an inductor L_(X) that is generally selected for goodperformance over a selected sub-band of a wideband RF input signal. Forexample, for a wideband from about 1.4 GHz to about 2.7 GHz, a firstinductor L₁ may be selected for good performance from about 1.8 GHz toabout 2.7 GHz, and a second inductor L₂ may be selected for goodperformance from about 1.4 GHz to about 1.7 GHz. The inductors L_(X) maybe internal to an IC chip embodiment, or may be a component external toan IC chip embodiment and coupled to the remaining circuitry of theswitched inductor tuning block 214 via solder bumps, wire bonds, or thelike, or may be a combination of internal and external inductors.

The inductor L_(X) of each branch X is coupled between a series switchSw1 _(X) on an RF_(IN) input port side and a series switch Sw2 _(X) onan RF_(OUT) output port side. Coupled between respective ends of theinductor L_(X) and circuit ground are respective shunt switches Sw3 _(X)and Sw4 _(X). Having shunt switches Sw3 _(X) and Sw4 _(X) on both sidesof the inductor L_(X) provides good isolation, since the series switchesSw1 _(X), Sw2 _(X) may exhibit a capacitance, C_(OFF), when opened thatmay adversely affect the performance of the LNA 216.

The operation of a selected branch X within the switched inductor tuningblock 214 is straightforward. For example, if branch 1 is to be coupledin-circuit between the RF_(IN) and RF_(OUT) ports in a signal passagemode (i.e., branch 1 is selected), then switches Sw1 ₁ and Sw2 ₁ areclosed (turned ON) and switches Sw3 ₁ and Sw4 ₁ are opened (turned OFF).Conversely, if branch 1 is to be taken out-of-circuit from between theRF_(IN) and RF_(OUT) ports in an isolation mode (i.e., branch 1 isdeselected), then switches Sw1 ₁ and Sw2 ₁ are opened and switches Sw3 ₁and Sw4 ₁ are closed.

Of note, more than one branch X may be in-circuit at a time. Forexample, in a two branch embodiment of the switched inductor tuningblock 214, four connection possibilities exist: branches 1 and 2 aredeselected; branch 1 is selected and branch 2 is deselected; branch 1 isdeselected and branch 2 is selected; or branches 1 and 2 are bothselected. Thus, three inductance states can be selected for a signalpath from RF_(IN) to RF_(OUT) in a two-branch switched inductor tuningblock 214: inductor L₁ alone, inductor L₂ alone, or inductors L₁ and L₂in parallel. As should be clear, additional combinations of inductorsL_(X) can be created for a switched inductor tuning block 214 havingmore than two branches X.

FIG. 4 is a circuit diagram 400 of one embodiment of one branch X forthe switched inductor tuning block 214 of FIG. 3, using field effecttransistors (FETs) for switches. In the illustrated example, each of theseries switches Sw1 _(X), Sw2 _(X) are implemented as single FETs, suchas MOSFETs. In some embodiments, the series switches Sw1 _(X), Sw2 _(X)may be implemented as two or more series coupled FETs. The shuntswitches Sw3 _(X), Sw4 _(X) are shown implemented as one or more FETscoupled in series (also known as a “stack”) between respective ends ofthe inductor L_(X) and circuit ground. If more than one FET in series isused for the series switches Sw1 _(X), Sw2 _(X) or the shunt switchesSw3 _(X), Sw4 _(X), each FET in the series is controlled by the samecontrol signal, and thus the series of FETs behaves like a singleswitch. In this example, the inductor L_(X) is shown connected by dashedlines, indicating that the inductor L_(X) is external to an ICembodiment of the switches Sw1 _(X), Sw2 _(X), Sw3 _(X), Sw4 _(X) (someor all of which may be integrated on the IC embodiment with the LNA 216and some or all of the additional circuitry shown in FIG. 2 surroundingthe LNA 216).

One benefit of stacking FETs for the shunt switches Sw3 _(X), Sw4 _(X)is that stacked FETs can withstand a higher voltage than a single FETwhen in the OFF state, which provides protection, for example, fromelectrostatic discharge (ESD) events. Stacking FETs also increases RFpower handling and improves linearity.

One advantage of branch X embodiments like the example shown in FIG. 4is that an applied RF_(IN) signal passes through only one inductor,whereas if two or more inductors are used in series, at least one ofwhich is bypassable, the OFF (bypassed) inductor(s) will have a lower Qfactor than a single inductor and suffer higher module parasitics.

For practical reasons, it may be desirable to tradeoff the OFF statecapacitance, CUFF, against the ON state resistance, R_(ON), of each FET.Thus, for example, the switch Sw2 _(X) nearest the LNA 216 generallyshould have a low C_(OFF) and a low R_(ON), since the LNA 216 issensitive to capacitance but the impedance of the signal path alsoshould be kept low. On the other hand, the switch Sw1 _(X) furthest fromthe LNA 216 may favor a low R_(ON) over a low C_(OFF), to lower theimpedance of the signal path on the ON state, while C_(OFF) can berelatively higher. Accordingly, the FET comprising switch Sw2 _(X)generally should be smaller than the FET comprising switch Sw1 _(X); forexample, Sw2 _(X) may have a total width about half the total width ofSw1 _(X). As another example, the FET or FETs implementing the shuntswitches Sw3 _(X), Sw4 _(X) generally should have a low CUFF, againbecause the LNA 216 is sensitive to capacitance. As frequency increases,the FET comprising switch Sw2 _(X) can be made even smaller relative tothe FET comprising switch Sw1 _(X); conversely, as frequency decreases,the FET comprising switch Sw2 _(X) will generally be larger relative tothe FET comprising switch Sw1 _(X).

A modeled embodiment of the single-LNA amplifier circuit 200 of FIG. 2,using a MOSFET implementation of the switched inductor tuning block 214in accordance with FIG. 4, exhibits a gain of about 20 dB over a 1300MHz tuning range (from 1.4 GHz to about 2.7 GHz), with an NF of lessthan about 1.2 dB. Using only a single LNA keeps an IC die size smallerthan a multiple-LNA solution, while requiring only two connections(e.g., solder bumps) per external tuning inductor L_(X).

It should be noted that embodiments of the switched inductor tuningblock 214 may be used with other types of broadband amplifiers,including power amplifiers. In addition, in some embodiments, theswitched inductor tuning block 214 may be coupled to the output of anamplifier, for example, for impedance matching or power matching. Moregenerally, a switched inductor tuning block 214 may be used anywhere inan amplifier circuit having a signal path that needs different inductorvalues for different modes of operation and which requires decentisolation and/or less correlation among those signal paths.

While FIG. 2 shows the switched inductor tuning block 214 coupled to asingle LNA 216, embodiments may include multiple LNA's selectivelycouplable to the switched inductor tuning block 214. For example, FIG.5A is a block diagram 500 showing a first configuration of multiple LNAs216 ₁-216 _(n) coupled to the RF_(OUT) port of a switched inductortuning block 214 through corresponding series switchesSw_(LNA1)-Sw_(LNAn). In the illustrated example, a particular LNA 216₁-216 _(N) may be coupled to any inductor L1-Ln by selecting an inductorsignal path, as described above, and closing the series switchcorresponding to the particular LNA while opening the series switchescorresponding to the other LNAs. Optional shunt switches Sh1-Shn may becoupled to the respective inputs of the LNAs 216 ₁-216 _(n) to provideeven better isolation by opening the shunt switch corresponding to theparticular LNA while closing the shunt switches corresponding to theother LNAs.

FIG. 5B is a block diagram 520 showing a second configuration ofmultiple LNAs 216 ₁-216 _(n) coupled to a switched inductor tuning block214 through a switching matrix 522. In the illustrated example, theinput of any LNA 216 ₁-216 _(n) may be coupled to any inductor L₁-Lnthrough a corresponding switch Sw2 ₁₋₁-Sw2 _(1-n), Sw2 _(n-1)-Sw2_(n-n). Shunt switches Sh1-Shn coupled to the respective inputs of theLNAs 216 ₁-216 _(n), when closed, provide isolation of non-selectedLNAs. An advantage of the matrix-switch configuration of FIG. 5B is thata signal propagated through a selected inductor Lx passes through onlyone switch before being applied to the input of a selected LNAx.

System Aspects

Embodiments of the present invention are useful in a wide variety oflarger radio frequency (RF) circuits and systems for performing a rangeof functions, including (but not limited to) impedance matchingcircuits, RF power amplifiers, RF low-noise amplifiers (LNAs), phaseshifters, attenuators, antenna beam-steering systems, charge pumpdevices, RF switches, etc. Such functions are useful in a variety ofapplications, such as radar systems (including phased array andautomotive radar systems), radio systems (including cellular radiosystems), and test equipment.

Radio system usage includes wireless RF systems (including basestations, relay stations, and hand-held transceivers) that use varioustechnologies and protocols, including various types of orthogonalfrequency-division multiplexing (“OFDM”), quadrature amplitudemodulation (“QAM”), Code-Division Multiple Access (“CDMA”),Time-Division Multiple Access (“TDMA”), Wide Band Code Division MultipleAccess (“W-CDMA”), Global System for Mobile Communications (“GSM”), LongTerm Evolution (“LTE”), 5G, and WiFi (e.g., 802.11a, b, g, ac, ax), aswell as other radio communication standards and protocols.

As an example of wireless RF system usage, FIG. 6 illustrates anexemplary prior art wireless communication environment 600 includingdifferent wireless communication systems 602 and 604, and may includeone or more mobile wireless devices 606.

A wireless device 606 may be capable of communicating with multiplewireless communication systems 602, 604 using one or more of thetelecommunication protocols noted above. A wireless device 606 also maybe capable of communicating with one or more satellites 608, such asnavigation satellites (e.g., GPS) and/or telecommunication satellites.The wireless device 606 may be equipped with multiple antennas,externally and/or internally, for operation on different frequenciesand/or to provide diversity against deleterious path effects such asfading and multipath interference. A wireless device 606 may be acellular phone, a personal digital assistant (PDA), a wireless-enabledcomputer or tablet, or some other wireless communication unit or device.A wireless device 606 may also be referred to as a mobile station, userequipment, an access terminal, or some other terminology.

The wireless system 602 may be, for example, a CDMA-based system thatincludes one or more base station transceivers (BSTs) 610 and at leastone switching center (SC) 612. Each BST 610 provides over-the-air RFcommunication for wireless devices 606 within its coverage area. The SC612 couples to one or more BSTs in the wireless system 602 and providescoordination and control for those BSTs.

The wireless system 604 may be, for example, a TDMA-based system thatincludes one or more transceiver nodes 614 and a network center (NC)616. Each transceiver node 614 provides over-the-air RF communicationfor wireless devices 606 within its coverage area. The NC 616 couples toone or more transceiver nodes 614 in the wireless system 604 andprovides coordination and control for those transceiver nodes 614.

In general, each BST 610 and transceiver node 614 is a fixed stationthat provides communication coverage for wireless devices 606, and mayalso be referred to as base stations or some other terminology. The SC612 and the NC 616 are network entities that provide coordination andcontrol for the base stations and may also be referred to by otherterminologies.

An important aspect of any wireless system, including the systems shownin FIG. 7, is in the details of how the component elements of the systemperform. FIG. 7 is a block diagram of a transceiver 700 that might beused in a wireless device, such as a cellular telephone, and which maybeneficially incorporate an embodiment of the present invention forimproved performance at a small IC chip size. As illustrated, thetransceiver 700 includes a mix of RF analog circuitry for directlyconveying and/or transforming signals on an RF signal path, non-RFanalog circuitry for operational needs outside of the RF signal path(e.g., for bias voltages and switching signals), and digital circuitryfor control and user interface requirements. In this example, a receiverpath Rx includes RF Front End, IF Block, Back-End, and Baseband sections(noting that in some implementations, the differentiation betweensections may be different).

The receiver path Rx receives over-the-air RF signals through an antenna702 and a switching unit 704, which may be implemented with activeswitching devices (e.g., field effect transistors or FETs), or withpassive devices that implement frequency-domain multiplexing, such as adiplexer or duplexer. An RF filter 706 passes desired received RFsignals to a low noise amplifier (LNA) circuit 708, the output of whichis combined in a mixer 710 with the output of a first local oscillator712 to produce an intermediate frequency (IF) signal. The LNA circuit708 may be, for example, an embodiment of the LNA circuit 200 of FIG. 2using a MOSFET implementation of the switched inductor tuning block 214in accordance with FIG. 4.

The IF signal may be amplified by an IF amplifier 714 and subjected toan IF filter 716 before being applied to a demodulator 718, which may becoupled to a second local oscillator 720. The demodulated output of thedemodulator 718 is transformed to a digital signal by ananalog-to-digital converter 722 and provided to one or more systemcomponents 724 (e.g., baseband signal processing, a video graphicscircuit, a sound circuit, memory devices, etc.). The converted digitalsignal may represent, for example, video or still images, sounds, orsymbols, such as text or other characters.

In the illustrated example, a transmitter path Tx includes Baseband,Back-End, IF Block, and RF Front End sections (again, in someimplementations, the differentiation between sections may be different).Digital data from one or more system components 724 is transformed to ananalog signal by a digital-to-analog converter 726, the output of whichis applied to a modulator 728, which also may be coupled to the secondlocal oscillator 720. The modulated output of the modulator 728 may besubjected to an IF filter 730 before being amplified by an IF amplifier732. The output of the IF amplifier 732 is then combined in a mixer 734with the output of the first local oscillator 712 to produce an RFsignal. The RF signal may be amplified by a driver 736, the output ofwhich is applied to a power amplifier (PA) 738. The amplified RF signalmay be coupled to an RF filter 740, the output of which is coupled tothe antenna 702 through the switching unit 704.

The operation of the transceiver 700 is controlled by a microprocessor742 in known fashion, which interacts with system control components(e.g., user interfaces, memory/storage devices, application programs,operating system software, power control, etc.). In addition, thetransceiver 700 will generally include other circuitry, such as biascircuitry 746 (which may be distributed throughout the transceiver 700in proximity to transistor devices), electro-static discharge (ESD)protection circuits, testing circuits (not shown), factory programminginterfaces (not shown), etc.

In modern transceivers, there are often more than one receiver path Rxand transmitter path Tx, for example, to accommodate multiplefrequencies and/or signaling modalities. Further, as should be apparentto one of ordinary skill in the art, some components of the transceiver700 may be in a positioned in a different order (e.g., filters) oromitted. Other components can be (and usually are) added (e.g.,additional filters, impedance matching networks, variable phaseshifters/attenuators, power dividers, etc.).

As discussed above, amplifiers in accordance with the present inventionprovide wideband coverage, high gain, a low noise factor (NF), smallsize, and low cost. As a person of ordinary skill in the art willunderstand, the system architecture of a transceiver utilizingembodiments of the present invention and of products incorporating suchtransceivers is beneficially impacted by the current invention incritical ways, including high performance, small overall IC chip size,and lower cost. These system-level improvements are specifically enabledby the current invention and may be critical to the overall solutionshown in FIG. 7 for many applications. The current invention thereforespecifically defines a system-level embodiment that is creativelyenabled by its inclusion in that system.

Methods

Another aspect of the invention includes methods of providing a widebandradio frequency (RF) signal to at least one amplifier. For example, FIG.8 is a process flow chart 800 showing one method of providing a widebandradio frequency (RF) signal to at least one amplifier. The methodincludes: selectively coupling at least one of a plurality ofinductances in series with an input signal path (Block 802); receivingthe RF signal in at least one selected amplifier after passage throughthe selected coupled inductance (Block 804); and outputting an amplifiedversion of the received RF signal (Block 806).

Fabrication Technologies & Options

The term “MOSFET”, as used in this disclosure, includes any field effecttransistor (FET) having an insulated gate whose voltage determines theconductivity of the transistor, and encompasses insulated gates having ametal or metal-like, insulator, and/or semiconductor structure. Theterms “metal” or “metal-like” include at least one electricallyconductive material (such as aluminum, copper, or other metal, or highlydoped polysilicon, graphene, or other electrical conductor), “insulator”includes at least one insulating material (such as silicon oxide orother dielectric material), and “semiconductor” includes at least onesemiconductor material.

As used in this disclosure, the term “radio frequency” (RF) refers to arate of oscillation in the range of about 3 kHz to about 300 GHz. Thisterm also includes the frequencies used in wireless communicationsystems. An RF frequency may be the frequency of an electromagnetic waveor of an alternating voltage or current in a circuit.

Various embodiments of the invention can be implemented to meet a widevariety of specifications. Unless otherwise noted above, selection ofsuitable component values is a matter of design choice. Variousembodiments of the invention may be implemented in any suitableintegrated circuit (IC) technology (including but not limited to MOSFETstructures), or in hybrid or discrete circuit forms. Integrated circuitembodiments may be fabricated using any suitable substrates andprocesses, including but not limited to bulk silicon,silicon-on-insulator (SOI), and silicon-on-sapphire (SOS). Unlessotherwise noted above, embodiments of the invention may be implementedin other transistor technologies such as bipolar, BiCMOS, LDMOS, BCD,GaAs HBT, GaN HEMT, GaAs pHEMT, and MESFET technologies. However,embodiments of the invention are particularly useful when fabricatedusing an SOI or SOS based process, or when fabricated with processeshaving similar characteristics. Fabrication in CMOS using SOI or SOSprocesses enables circuits with low power consumption, the ability towithstand high power signals during operation due to FET stacking, goodlinearity, and high frequency operation (i.e., radio frequencies up toand exceeding 50 GHz). Monolithic IC implementation is particularlyuseful since parasitic capacitances generally can be kept low (or at aminimum, kept uniform across all units, permitting them to becompensated) by careful design.

Voltage levels may be adjusted, and/or voltage and/or logic signalpolarities reversed, depending on a particular specification and/orimplementing technology (e.g., NMOS, PMOS, or CMOS, and enhancement modeor depletion mode transistor devices). Component voltage, current, andpower handling capabilities may be adapted as needed, for example, byadjusting device sizes, serially “stacking” components (particularlyFETs) to withstand greater voltages, and/or using multiple components inparallel to handle greater currents. Additional circuit components maybe added to enhance the capabilities of the disclosed circuits and/or toprovide additional functionality without significantly altering thefunctionality of the disclosed circuits.

Circuits and devices in accordance with the present invention may beused alone or in combination with other components, circuits, anddevices. Embodiments of the present invention may be fabricated asintegrated circuits (ICs), which may be encased in IC packages and/or inmodules for ease of handling, manufacture, and/or improved performance.In particular, IC embodiments of this invention are often used inmodules in which one or more of such ICs are combined with other circuitblocks (e.g., filters, amplifiers, passive components, and possiblyadditional ICs) into one package. The ICs and/or modules are thentypically combined with other components, often on a printed circuitboard, to form an end product such as a cellular telephone, laptopcomputer, or electronic tablet, or to form a higher level module whichmay be used in a wide variety of products, such as vehicles, testequipment, medical devices, etc. Through various configurations ofmodules and assemblies, such ICs typically enable a mode ofcommunication, often wireless communication.

CONCLUSION

A number of embodiments of the invention have been described. It is tobe understood that various modifications may be made without departingfrom the spirit and scope of the invention. For example, some of thesteps described above may be order independent, and thus can beperformed in an order different from that described. Further, some ofthe steps described above may be optional. Various activities describedwith respect to the methods identified above can be executed inrepetitive, serial, and/or parallel fashion.

It is to be understood that the foregoing description is intended toillustrate and not to limit the scope of the invention, which is definedby the scope of the following claims, and that other embodiments arewithin the scope of the claims. In particular, the scope of theinvention includes any and all feasible combinations of one or more ofthe processes, machines, manufactures, or compositions of matter setforth in the claims below. (Note that the parenthetical labels for claimelements are for ease of referring to such elements, and do not inthemselves indicate a particular required ordering or enumeration ofelements; further, such labels may be reused in dependent claims asreferences to additional elements without being regarded as starting aconflicting labeling sequence).

What is claimed is:
 1. An amplifier circuit including: (a) an inputsignal path for receiving a wideband radio frequency (RF) signal; (b) aswitched inductor tuning block coupled to the input signal path andconfigured to selectively couple at least one of a plurality ofinductances in series with the input signal path; and (c) at least oneamplifier, each amplifier having an input coupled to the switchedinductor tuning block and configured to receive the RF signal afterpassage through a selected one of the plurality of inductances, and anoutput for providing an amplified version of the RF signal.
 2. Theinvention of claim 1, wherein the switched inductor tuning blockincludes a plurality of selectable branches, each branch including: (a)an RF signal input switch; (b) an RF signal output switch; (c) aninductor coupled between the RF signal input switch and the RF signaloutput switch; (d) a first shunt switch coupled between a first terminalof the inductor and circuit ground; and (e) a second shunt switchcoupled between a second terminal of the inductor and circuit ground. 3.The invention of claim 2, wherein each of the switches comprises atleast one field effect transistor.
 4. The invention of claim 3, whereinthe total width of the at least one field effect transistor comprisingthe RF signal output switch is less than the total width of the at leastone field effect transistor comprising the RF signal input switch. 5.The invention of claim 3, wherein each of the switches comprises aMOSFET fabricated by a silicon-on-insulator process.
 6. The invention ofclaim 2, wherein each of the switches comprises at least one fieldeffect transistor embodied in an integrated circuit configured to becoupled to the inductor as an external component.
 7. The invention ofclaim 2, wherein each of the RF signal input switch and the RF signaloutput switch comprise a field effect transistor, and each of the firstshunt switch and the second shunt switch comprise at least twoseries-coupled field effect transistors.
 8. The invention of claim 2,wherein in a signal passage mode for a branch when selected, the RFsignal input switch and the RF signal output switch are CLOSED and thefirst and second shunt switch are OPEN, and in an isolation mode for thebranch when not selected, the RF signal input switch and the RF signaloutput switch are OPEN and the first and second shunt switch are CLOSED.9. The invention of claim 2, wherein more than one of the plurality ofselectable branches may be selected at one time.
 10. A low-noiseamplifier circuit including: (a) an input signal path for receiving awideband radio frequency (RF) signal; (b) a switched inductor tuningblock coupled to the input signal path and configured to selectivelycouple at least one of a plurality of inductances in series with theinput signal path, the switched inductor tuning block including aplurality of selectable branches, each branch including: (1) an RFsignal input switch; (2) an RF signal output switch; (3) an inductorcoupled between the RF signal input switch and the RF signal outputswitch; (4) a first shunt switch coupled between a first terminal of theinductor and circuit ground; (5) a second shunt switch coupled between asecond terminal of the inductor and circuit ground; and (c) at least onelow-noise amplifier, each low-noise amplifier having an input coupled tothe switched inductor tuning block and configured to receive the RFsignal after passage through a selected one of the plurality ofinductances, and an output for providing an amplified version of the RFsignal.
 11. The invention of claim 10, wherein each of the switchescomprises at least one field effect transistor.
 12. The invention ofclaim 11, wherein the total width of the at least one field effecttransistor comprising the RF signal output switch is less than the totalwidth of the at least one field effect transistor comprising the RFsignal input switch.
 13. The invention of claim 11, wherein each of theswitches comprises a MOSFET fabricated by a silicon-on-insulatorprocess.
 14. The invention of claim 10, wherein each of the switchescomprises at least one field effect transistor embodied in an integratedcircuit configured to be coupled to the inductor as an externalcomponent.
 15. The invention of claim 10, wherein each of the RF signalinput switch and the RF signal output switch comprise a field effecttransistor, and each of the first shunt switch and the second shuntswitch comprise at least two series-coupled field effect transistors.16. The invention of claim 10, wherein in a signal passage mode for abranch when selected, the RF signal input switch and the RF signaloutput switch are CLOSED and the first and second shunt switch are OPEN,and in an isolation mode for the branch when not selected, the RF signalinput switch and the RF signal output switch are OPEN and the first andsecond shunt switch are CLOSED.
 17. The invention of claim 10, whereinmore than one of the plurality of selectable branches may be selected atone time.
 18. A low-noise amplifier circuit including: (a) an inputsignal path for receiving a wideband radio frequency (RF) signal; (b) aswitched inductor tuning block coupled to the input signal path andconfigured to selectively couple at least one of a plurality ofinductances in series with the input signal path, the switched inductortuning block including a plurality of selectable branches, each branchincluding: (1) an RF signal input comprising at least one series-coupledfield effect transistor (FET) switch; (2) an RF signal output switchcomprising at least one series-coupled FET; (3) an inductor coupledbetween the RF signal input switch and the RF signal output switch; (4)a first shunt switch coupled between a first terminal of the inductorand circuit ground and comprising at least one series-coupled FET; (5) asecond shunt switch coupled between a second terminal of the inductorand circuit ground and comprising at least one series-coupled FET; and(c) at least one low-noise amplifier, each low-noise amplifier having aninput coupled to the switched inductor tuning block and configured toreceive the RF signal after passage through a selected one of theplurality of inductances, and an output for providing an amplifiedversion of the RF signal.
 19. The invention of claim 18, wherein theFETs are embodied in an integrated circuit configured to be coupled tothe inductor as an external component.
 20. The invention of claim 18,wherein each of the RF signal input switch and the RF signal outputswitch comprise one field effect transistor, and each of the first shuntswitch and the second shunt switch comprise at least two series-coupledfield effect transistors.
 21. The invention of claim 18, wherein in asignal passage mode for a branch when selected, the RF signal inputswitch and the RF signal output switch are CLOSED and the first andsecond shunt switch are OPEN, and in an isolation mode for the branchwhen not selected, the RF signal input switch and the RF signal outputswitch are OPEN and the first and second shunt switch are CLOSED. 22.The invention of claim 18, wherein more than one of the plurality ofselectable branches may be selected at one time.
 23. An amplifiercircuit including: (a) an input signal path for receiving a widebandradio frequency (RF) signal; (b) a switched inductor tuning blockcoupled to the input signal path and configured to selectively couple atleast one of a plurality of inductances in series with the input signalpath, the switched inductor tuning block including a plurality ofselectable branches, each branch including: (1) an RF signal inputswitch; (2) an RF signal output switch; (3) an inductor coupled betweenthe RF signal input switch and the RF signal output switch; (4) a firstshunt switch coupled between a first terminal of the inductor andcircuit ground; and (5) a second shunt switch coupled between a secondterminal of the inductor and circuit ground; and (c) at least oneamplifier, each amplifier having an input coupled to the switchedinductor tuning block through a respective series switch, each amplifierconfigured to receive the RF signal after passage through a selected oneof the plurality of inductances, and an output for providing anamplified version of the RF signal.
 24. An amplifier circuit including:(a) an input signal path for receiving a wideband radio frequency (RF)signal; (b) a switched inductor tuning block coupled to the input signalpath and configured to selectively couple at least one of a plurality ofinductances in series with the input signal path, the switched inductortuning block including a plurality of selectable branches, each branchincluding: (1) an RF signal input switch; (2) an inductor coupled to theRF signal input switch; (3) a first shunt switch coupled between a firstterminal of the inductor and circuit ground; and (4) a second shuntswitch coupled between a second terminal of the inductor and circuitground; and (c) a plurality of amplifiers, each amplifier having aninput coupled to the second terminal of each inductor within theplurality of selectable branches of the switched inductor tuning blockthrough a switching matrix, each amplifier configured to receive the RFsignal after passage through a selected one of the plurality ofinductances, and an output for providing an amplified version of the RFsignal.
 25. A method of providing a wideband radio frequency (RF) signalto at least one amplifier, including: (a) selectively coupling at leastone of a plurality of inductances in series with an input signal path;and (b) receiving the RF signal in at least one selected amplifier afterpassage through the selected coupled inductance; and (c) outputting anamplified version of the received RF signal.